It is quite common to administer a drug to a patient over time by first diluting the drug in a liquid vehicle such as saline. Generally, the drug is mixed with the liquid vehicle, and the resulting solution is then administered intravenously to the patient. However, once mixed, the concentration of the drug in the solution remains relatively constant and only the administration rate of the solution can be adjusted.
To allow changes in drug concentrations, devices that mix the drug with the liquid vehicle have been developed. These devices use roller clamps to separately control the drip rates of the drug and liquid vehicle into a mixing chamber. Once the roller clamps are set, the mixing ratio remains the same until someone changes the settings. Even this type of system does not allow for the periodic automatic administration of a bolus of drug.
Other devices provide for the sequential administration of a drug followed by a physiologically tolerable liquid carrier such as saline. Such systems provide for the automatic switching to the saline after the drug has been administered. Unfortunately, none of these devices provide for timing or variable control of the administration of the drug to the patient.
It is sometimes desirable to administer a bolus of a particular drug at given times to the patient. Present devices for such administration rely on electrical timer systems that operate mechanical valves. The rates and time of drug administration are set in the device, and the valves are opened and closed automatically. However, such devices are relatively complicated and rely on the operation of a mechanical valve having the inherent disadvantage of possible failure through valve malfunction.
What is needed is a system and method for delivering a therapeutic agent to a patient which is easily adjustable without the need of mechanical means. Such a device should allow for the easy control of administration rates as well as times of administration. The present invention meets these desires.